WO2010084912A1 - Waterproofing sound-transmitting film, process for producing same, and electrical product employing same - Google Patents

Waterproofing sound-transmitting film, process for producing same, and electrical product employing same Download PDF

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WO2010084912A1
WO2010084912A1 PCT/JP2010/050711 JP2010050711W WO2010084912A1 WO 2010084912 A1 WO2010084912 A1 WO 2010084912A1 JP 2010050711 W JP2010050711 W JP 2010050711W WO 2010084912 A1 WO2010084912 A1 WO 2010084912A1
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ptfe
sound
permeable membrane
waterproof sound
porous
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PCT/JP2010/050711
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French (fr)
Japanese (ja)
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堀江百合
阿部悠一
古内浩二
瀧石公正
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日東電工株式会社
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Priority to EP10733519.2A priority Critical patent/EP2351647B1/en
Priority to KR1020117007080A priority patent/KR101249195B1/en
Priority to CN2010800023291A priority patent/CN102123863B/en
Publication of WO2010084912A1 publication Critical patent/WO2010084912A1/en
Priority to US13/009,510 priority patent/US8272517B2/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/32—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed at least two layers being foamed and next to each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/36—Polytetrafluoroethene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B32B27/322—Layered products comprising a layer of synthetic resin comprising polyolefins comprising halogenated polyolefins, e.g. PTFE
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
    • H04R31/003—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor for diaphragms or their outer suspension
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/24—All layers being polymeric
    • B32B2250/246—All polymers belonging to those covered by groups B32B27/32 and B32B27/30
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2264/00—Composition or properties of particles which form a particulate layer or are present as additives
    • B32B2264/02—Synthetic macromolecular particles
    • B32B2264/0214—Particles made of materials belonging to B32B27/00
    • B32B2264/0257—Polyolefin particles, e.g. polyethylene or polypropylene homopolymers or ethylene-propylene copolymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/02—Cellular or porous
    • B32B2305/026—Porous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2305/00—Condition, form or state of the layers or laminate
    • B32B2305/80—Sintered
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/10—Properties of the layers or laminate having particular acoustical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/54—Yield strength; Tensile strength
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/558—Impact strength, toughness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/726—Permeability to liquids, absorption
    • B32B2307/7265—Non-permeable
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2231/00—Details of apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor covered by H04R31/00, not provided for in its subgroups
    • H04R2231/001—Moulding aspects of diaphragm or surround
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2307/00—Details of diaphragms or cones for electromechanical transducers, their suspension or their manufacture covered by H04R7/00 or H04R31/003, not provided for in any of its subgroups
    • H04R2307/025—Diaphragms comprising polymeric materials

Abstract

A waterproofing sound-transmitting film which comprises a polytetrafluoroethylene (PTFE) porous film and the waterproofing properties of which have been further improved while keeping the sound-transmitting properties as much intact as possible.  The waterproofing sound-transmitting film comprises a PTFE porous film, the PTFE porous film being composed of a first porous layer and a second porous layer that has been laminated to the first porous layer on the basis of a binding power acting between the PTFE matrixes.  The first and second porous layers are constituted of PTFE having a number-average molecular weight as determined by the standard specific-gravity method of 5.0×107 or higher.  The first porous layer and/or the second porous layer has an average pore diameter of 1 µm or smaller.  The waterproofing sound-transmitting film has a surface density of 1-10 g/m2 and a tensile strength of 10-100 MPa, and the value obtained by dividing the piercing strength of the waterproofing sound-transmitting film by the surface density of the film is 25-50 kPa·m2/g.

Description

防水通音膜とその製造方法ならびにそれを用いた電気製品Waterproof sound-permeable membrane, method for producing the same, and electrical product using the same
　本発明は、音声機能を備えた電気製品に使用される防水通音膜と、その製造方法とに関する。本発明は、さらに、その防水通音膜を用いた電気製品に関する。 The present invention relates to a waterproof sound-permeable membrane used for an electrical product having a voice function, and a manufacturing method thereof. The present invention further relates to an electrical product using the waterproof sound-permeable membrane.
　携帯電話、ノートパソコン、電子手帳、デジタルカメラ、ゲーム機器といった電気製品は、しばしば屋外で使用されるため、防水構造とすることが望まれる。電気製品において防水構造とすることが最も困難な部分は、スピーカ、マイク、ブザーなどの発音部および受音部である。音声機能を備えた電気製品の筐体には、通常、発音部および受音部に対応する位置に開口が設けられ、この開口において、発音部および受音部と外部との間で音声が伝達される。 Since electrical products such as mobile phones, notebook computers, electronic notebooks, digital cameras, and game machines are often used outdoors, it is desirable to have a waterproof structure. The most difficult part of an electrical product to have a waterproof structure is a sound generator and a sound receiver such as a speaker, a microphone, and a buzzer. The housing of an electrical product having a sound function is usually provided with openings at positions corresponding to the sound generation unit and the sound reception unit, and sound is transmitted between the sound generation unit and the sound reception unit and the outside through this opening. Is done.
　良好な通音性を確保しつつ、発音部および受音部のための開口から筐体内部への水の侵入を防ぐ部材として、防水通音膜が知られている。防水通音膜は、音の透過を阻害しにくい材料からなる薄膜である。筐体に設けられた開口を防水通音膜で塞ぐことにより、当該開口における通音性と防水性との両立を図ることができる。防水通音膜には、ポリテトラフルオロエチレン（ＰＴＦＥ）多孔質膜が好適である（特開2004-83811号公報参照）。 A waterproof sound-permeable membrane is known as a member that prevents the entry of water from the opening for the sound generation part and the sound receiving part into the inside of the housing while ensuring good sound permeability. The waterproof sound-permeable membrane is a thin film made of a material that does not obstruct sound transmission. By closing the opening provided in the housing with a waterproof sound-permeable membrane, it is possible to achieve both sound permeability and waterproofness in the opening. As the waterproof sound-permeable membrane, a polytetrafluoroethylene (PTFE) porous membrane is suitable (see Japanese Patent Application Laid-Open No. 2004-83811).
　ＰＴＦＥ多孔質膜の平均孔径を小さくすると、当該膜の防水性が向上する一方で、膜の面密度が大きくなって通音性が低下する。即ち、防水通音膜における防水性と通音性とはトレードオフの関係にあり、通音性を低下させることなく防水性を高めることは容易ではない。特開2004-83811号公報では、ＰＴＦＥ多孔質膜の平均孔径と面密度とを規定することで、防水性と通音性との両立が図られている。 When the average pore diameter of the PTFE porous membrane is reduced, the waterproof property of the membrane is improved, while the surface density of the membrane is increased and the sound transmission property is lowered. That is, there is a trade-off relationship between waterproofness and sound permeability in the waterproof sound-permeable membrane, and it is not easy to improve waterproofness without reducing sound permeability. In Japanese Patent Application Laid-Open No. 2004-83811, both the waterproof property and the sound permeability are achieved by defining the average pore diameter and the surface density of the PTFE porous membrane.
　近年、電気製品に求められる防水性は、年を追うごとに高まってきている。具体的には、生活防水レベルにとどまらず、水中に浸漬可能なレベル、さらには所定の水深で一定時間の使用が可能なレベルの防水性が求められるようになってきている。しかし、特開2004-83811号公報に開示された防水通音膜は、電気製品が水に浸漬した状況までは想定していない。 In recent years, the waterproofness required for electrical products has been increasing year by year. Specifically, there is a demand for waterproofness that is not limited to the level of waterproofing for daily life but that can be immersed in water, and that can be used for a predetermined time at a predetermined depth. However, the waterproof sound-permeable membrane disclosed in Japanese Patent Application Laid-Open No. 2004-83811 does not assume a situation where an electrical product is immersed in water.
　ところで、特開平7-292144号公報には、防水通音膜ではないが、空気中の微粒子を除去するための高性能エアフィルター（いわゆるＵＬＰＡまたはＨＥＰＡフィルター）用ＰＴＦＥ複合多孔膜の製造方法が開示されている。特開平7-292144号公報に記載の製造方法（請求項参照）では、最初に、乳化重合法によって得られたＰＴＦＥ粉末および液状潤滑剤を含んでなる混合物をペースト押出成形してＰＴＦＥフィルムを形成する。次に、得られたフィルムをＰＴＦＥ焼成体の融点以下の温度で押出方向（長手方向、ＭＤ方向）に延伸することにより、少なくとも２枚の延伸されたＰＴＦＥフィルムが重なっている複合体を形成する。次に、得られた複合体を幅方向（長手方向に垂直な方向、ＴＤ方向）に延伸することにより、長手方向延伸および幅方向延伸による伸長面積倍率が少なくとも５０倍となるようにして延伸された複合体を形成する。最後に、必要に応じて、この複合体を熱固定して高性能エアフィルタを得る。また、特開平7-292144号公報には、上述した製造方法によって、圧力損失が小さく（通気性が高く）、孔径が小さく、ピンホールなどの欠陥部が非常に少ないＰＴＦＥ多孔質膜が得られること、ならびにこの多孔質膜が高性能エアフィルターに好適であることが記載されている（段落0014参照）。 By the way, JP-A-7-292144 discloses a method for producing a PTFE composite porous membrane for a high performance air filter (so-called ULPA or HEPA filter) for removing fine particles in the air, although it is not a waterproof sound-permeable membrane. Has been. In the production method described in JP-A-7-292144 (see claims), first, a PTFE film is formed by paste extrusion molding a mixture containing PTFE powder and liquid lubricant obtained by an emulsion polymerization method. To do. Next, the obtained film is stretched in the extrusion direction (longitudinal direction, MD direction) at a temperature equal to or lower than the melting point of the PTFE fired body to form a composite in which at least two stretched PTFE films overlap. . Next, the obtained composite is stretched in the width direction (direction perpendicular to the longitudinal direction, TD direction) so that the stretched area ratio by longitudinal stretching and width stretching is at least 50 times. To form a complex. Finally, if necessary, the composite is heat-set to obtain a high-performance air filter. Japanese Patent Laid-Open No. 7-292144 discloses that a PTFE porous membrane having a small pressure loss (high air permeability), a small hole diameter, and very few defects such as pinholes can be obtained by the above-described manufacturing method. And that this porous membrane is suitable for high performance air filters (see paragraph 0014).
特開2004-83811号公報JP 2004-83811 A 特開平7-292144号公報JP 7-292144 A
　本発明は、ＰＴＦＥ多孔質膜を含む防水通音膜であって、通音性をなるべく低下させることなく防水性をさらに向上させた、例えば水に浸漬可能な電気製品を実現できる、防水通音膜の提供を目的とする。 The present invention relates to a waterproof sound-permeable membrane including a porous PTFE membrane, which can realize an electrical product that can be immersed in water, for example, which can further improve the waterproof property without reducing the sound-permeable property as much as possible. The purpose is to provide a membrane.
　本発明者らは、水に浸漬可能な電気製品を実現するために、次のような検討結果を得た。 The present inventors obtained the following examination results in order to realize an electrical product that can be immersed in water.
　第１に、水への浸漬によって高い水圧が防水通音膜に一定時間以上加わると、水圧によって膜が伸び、膜の微孔が変形することで水が膜を透過したり、膜が破裂しやすくなったりする。ここで、一定の水圧にも耐えうるような高い防水性（耐水圧性）を実現するには、膜の引張強度が重要なファクターとなる。膜の面密度を大きくすれば引張強度も向上するが、面密度の増加により通音性が低下することは上述のとおりである。バッキング材のラミネートによる引張強度の向上も可能であるが、ラミネートしたバッキング材が防水通音膜の振動を阻害するために、通音性の極端な低下が生じる。なお、ここでいう「高い水圧」とは、一般に０．０１ＭＰａ以上、特に０．０５ＭＰａ以上、さらには０．１５ＭＰａ以上程度の水圧をいうが、これより低い値であっても長時間、膜に水圧が加わることによって、同様の現象が生じることがある。 First, when a high water pressure is applied to the waterproof sound-permeable membrane for a certain period of time by immersion in water, the membrane expands due to the water pressure, and the micropores of the membrane deform to cause water to permeate the membrane or rupture the membrane. It becomes easy. Here, the tensile strength of the membrane is an important factor for realizing high waterproofness (water pressure resistance) that can withstand a constant water pressure. If the surface density of the film is increased, the tensile strength is also improved. However, as described above, the sound permeability is lowered by increasing the surface density. Although it is possible to improve the tensile strength by laminating the backing material, the laminated backing material inhibits the vibration of the waterproof sound-permeable membrane, resulting in an extreme decrease in sound permeability. Incidentally, the “high water pressure” here generally means a water pressure of 0.01 MPa or more, particularly 0.05 MPa or more, and further about 0.15 MPa or more. A similar phenomenon may occur when water pressure is applied.
　第２に、防水通音膜は、通常、電気製品の筐体に設けられた開口に取り付けられるため、その表面が外部に露出している。このため、外部からの異物の接触による破損のおそれがある。膜が破損すると防水性が失われ、また、破損しないまでも膜の表面が傷ついたり膜が変形したりすれば、水圧が加わった際にそこを起点に水漏れや膜の破裂が生じやすくなる。この傾向は、通音性の確保を目的として防水通音膜の面密度を小さくした場合に、特に顕著である。ここで、外部からの異物の接触に対応するためには、膜の突き刺し強度が重要なファクターとなる。膜の面密度を大きくすれば突き刺し強度も向上するが、面密度の増加により通音性が低下することは上述のとおりである。 Second, since the waterproof sound-permeable membrane is usually attached to an opening provided in the housing of the electrical product, the surface thereof is exposed to the outside. For this reason, there exists a possibility of the damage by the contact of the foreign material from the outside. If the membrane breaks, the waterproofness is lost, and if the membrane surface is damaged or the membrane is deformed even if it is not damaged, water leakage or membrane rupture tends to occur when water pressure is applied. . This tendency is particularly remarkable when the surface density of the waterproof sound-permeable membrane is reduced for the purpose of ensuring sound permeability. Here, in order to cope with the contact of foreign matter from the outside, the piercing strength of the film is an important factor. If the surface density of the film is increased, the piercing strength is also improved. However, as described above, the sound permeability is lowered due to the increase of the surface density.
　本発明者らは、判明したこれら問題を鋭意検討し、本発明の防水通音膜を完成させた。本発明の防水通音膜は、ＰＴＦＥ多孔質膜を含む防水通音膜であって、前記ＰＴＦＥ多孔質膜が、第１多孔質層と、ＰＴＦＥのマトリクス間に働く結着力に基づいて前記第１多孔質層と積層および一体化された第２多孔質層とを備える。前記第１および第２多孔質層は、標準比重法により算出した数平均分子量が５．０×１０7以上のＰＴＦＥにより構成される。前記第１および第２多孔質層から選ばれる少なくとも１つの層の平均孔径は１μｍ以下である。前記防水通音膜の面密度は１～１０ｇ／ｍ2であり、前記防水通音膜の引張強度は１０～１００ＭＰａである。前記防水通音膜の突き刺し強度を当該膜の面密度で除した値が、２５～５０ｋＰａ・ｍ2／ｇである。 The present inventors diligently studied these problems, and completed the waterproof sound-permeable membrane of the present invention. The waterproof sound-permeable membrane of the present invention is a waterproof sound-permeable membrane including a PTFE porous membrane, wherein the PTFE porous membrane is based on the binding force acting between the first porous layer and the PTFE matrix. A first porous layer and a second porous layer laminated and integrated. The first and second porous layers are made of PTFE having a number average molecular weight calculated by a standard specific gravity method of 5.0 × 10 7 or more. The average pore diameter of at least one layer selected from the first and second porous layers is 1 μm or less. The surface density of the waterproof sound-permeable membrane is 1 to 10 g / m 2 , and the tensile strength of the waterproof sound-permeable membrane is 10 to 100 MPa. A value obtained by dividing the piercing strength of the waterproof sound-permeable membrane by the surface density of the membrane is 25 to 50 kPa · m 2 / g.
　本発明の製造方法は、上記本発明の防水通音膜の製造方法であって、標準比重法により算出した数平均分子量が５．０×１０7以上のＰＴＦＥからなるＰＴＦＥ微粉末と、加工助剤と、を含むペーストを押出成形する工程と、前記ペーストの成形体であるシートまたは前記ペーストの成形体を圧延して得られるシートを、ＰＴＦＥの融点未満の温度で第１方向に延伸する工程と、前記第１方向への延伸後のシートを複数枚重ね合わせる工程と、前記重ね合わせた複数枚のシートを、ＰＴＦＥの融点未満の温度で前記第１方向と交差する第２方向に延伸する工程と、前記第２方向への延伸後の複数枚のシートを、ＰＴＦＥの融点以上の温度で焼成して、ＰＴＦＥのマトリクス間に働く結着力に基づいて一体化する工程と、を含む。 The production method of the present invention is a method for producing the waterproof sound-permeable membrane of the present invention, wherein a PTFE fine powder comprising PTFE having a number average molecular weight of 5.0 × 10 7 or more calculated by a standard specific gravity method, and a processing aid. A step of extruding a paste containing an agent, and a step of stretching a sheet which is a molded body of the paste or a sheet obtained by rolling the molded body of the paste in a first direction at a temperature lower than the melting point of PTFE. And a step of superimposing a plurality of sheets stretched in the first direction, and stretching the superposed sheets in a second direction intersecting the first direction at a temperature lower than the melting point of PTFE. And a step of firing the plurality of sheets after stretching in the second direction at a temperature equal to or higher than the melting point of PTFE and integrating them based on the binding force acting between the PTFE matrices.
　他の側面から見た本発明の製造方法は、上記本発明の防水通音膜の製造方法であって、標準比重法により算出した数平均分子量が５．０×１０7以上のＰＴＦＥからなるＰＴＦＥ微粉末と、加工助剤と、を含むペーストを押出成形する工程と、前記ペーストの成形体であるシートまたは前記ペーストの成形体を圧延して得られるシートを、ＰＴＦＥの融点未満の温度で二軸延伸する工程と、前記二軸延伸後のシートを複数枚重ね合わせる工程と、前記重ね合わせた複数枚のシートを、ＰＴＦＥの融点以上の温度で焼成して、ＰＴＦＥのマトリクス間に働く結着力に基づいて一体化する工程と、を含む。 The production method of the present invention viewed from another aspect is a method for producing the waterproof sound-permeable membrane of the present invention, wherein the number average molecular weight calculated by the standard specific gravity method is PTFE composed of PTFE of 5.0 × 10 7 or more. A step of extruding a paste containing fine powder and a processing aid, and a sheet obtained by rolling the paste or the paste formed body at a temperature lower than the melting point of PTFE. A step of axial stretching, a step of superimposing a plurality of the biaxially stretched sheets, and a binding force that works between the PTFE matrices by firing the superposed multiple sheets at a temperature equal to or higher than the melting point of PTFE. And integrating them on the basis of
　本発明の電気製品は、音声機能を備えた電気製品であって、音声を出力するための発音部および音声を入力するための受音部から選ばれる少なくとも１つと、前記発音部および／または受音部と外部との間で音声を伝達できるとともに、前記発音部および／または受音部への水の侵入を抑制する防水通音膜とを備え、前記防水通音膜が上記本発明の防水通音膜である。 An electrical product according to the present invention is an electrical product having a voice function, wherein at least one selected from a sound generation unit for outputting sound and a sound reception unit for inputting sound, and the sound generation unit and / or reception unit. A waterproof sound-permeable membrane that can transmit sound between the sound portion and the outside and suppress water intrusion into the sound generation portion and / or the sound-receiving portion, and the waterproof sound-permeable membrane is waterproof according to the present invention. It is a sound-permeable membrane.
　上述したように、ＰＴＦＥ多孔質膜を含む防水通音膜の通音性および防水性を高いレベルで両立させるためには、ＰＴＦＥ多孔質膜の平均孔径を小さくするとともに面密度を低下させ、さらに、面密度を低く保ったまま、引張強度および突き刺し強度の向上を図らねばならない。 As described above, in order to achieve both the sound permeability and waterproofness of the waterproof sound-permeable membrane including the PTFE porous membrane at a high level, the average pore diameter of the PTFE porous membrane is reduced and the surface density is decreased. The tensile strength and puncture strength must be improved while keeping the surface density low.
　本発明の防水通音膜では、複数の多孔質層（ＰＴＦＥ多孔質層）を、防水通音膜としての面密度が１～１０ｇ／ｍ2となるように、積層および一体化している。ここで、少なくとも１つの多孔質層が、１μｍ以下の十分に小さい平均孔径を有する。そして、複数の多孔質層を積層および一体化していること、ならびに各多孔質層を、標準比重法により算出した数平均分子量が５．０×１０7以上のＰＴＦＥにより構成すること、によって、良好な通音性が得られる１～１０ｇ／ｍ2の範囲に面密度を低く保ちながらも、高い引張強度（１０～１００ＭＰａ）および突き刺し強度（面密度で除した値にして２５～５０ｋＰａ・ｍ2／ｇ）を実現している。 In the waterproof sound-permeable membrane of the present invention, a plurality of porous layers (PTFE porous layers) are laminated and integrated so that the surface density of the waterproof sound-permeable membrane is 1 to 10 g / m 2 . Here, at least one porous layer has a sufficiently small average pore diameter of 1 μm or less. And it is good by laminating | stacking and integrating several porous layers, and comprising each porous layer by PTFE whose number average molecular weight computed by the standard specific gravity method is 5.0x10 < 7 > or more. High tensile strength (10 to 100 MPa) and piercing strength (value divided by surface density, 25 to 50 kPa · m 2 ) while keeping the surface density low in the range of 1 to 10 g / m 2 where a good sound transmission is obtained. / G).
　面密度を低く保ったままＰＴＦＥ多孔質膜の強度を向上させる１つの方法として、当該膜の延伸倍率を高めることがある。なぜなら、ＰＴＦＥ多孔質膜は、延伸倍率が高くなるほどＰＴＦＥ分子の配向が進み、マトリクス強度が増加する傾向を示すからである。したがって、面密度が同一であっても、延伸倍率が低い膜と高い膜とを比較すると、後者の方が高強度となる。 One method for improving the strength of the PTFE porous membrane while keeping the surface density low is to increase the draw ratio of the membrane. This is because the PTFE porous membrane shows a tendency that the orientation of PTFE molecules advances and the matrix strength increases as the draw ratio increases. Therefore, even if the areal density is the same, when comparing a film having a low draw ratio with a film having a high draw ratio, the latter has a higher strength.
　また、面密度と延伸倍率とが同一である場合、単層膜と積層膜とでは、積層膜の方が高強度となる。例えば、厚さ２００μｍのＰＴＦＥシートを二軸延伸および積層して得られる２層膜と、厚さ４００μｍのＰＴＦＥシートを同倍率で二軸延伸して得られる単層膜とを比較した場合、両者の面密度および延伸倍率は等しくなるが、２層膜の方が高強度となる。それは以下の理由による。例えば、ペーストの成形体を圧延することによって延伸前のＰＴＦＥシートを得る場合において、厚さ２００μｍのＰＴＦＥシートを得るためにペーストの成形体に加えられる圧力は、厚さ４００μｍのＰＴＦＥシートを得るためにペーストの成形体に加えられる圧力よりも大きい。ペーストの成形体に加えられる圧力が大きいと、ＰＴＦＥ間に働く結着力が増大し、最終的に得られるＰＴＦＥ多孔質膜の強度も高くなる。圧延を行わない場合、例えば、Ｔダイによりペーストをシートに押出成形する場合も同様である。即ち、高強度のＰＴＦＥ多孔質膜を得るためには、延伸倍率だけではなく、延伸前のＰＴＦＥシートの加圧履歴が極めて重要である。 In addition, when the surface density and the draw ratio are the same, the laminated film has higher strength between the single-layer film and the laminated film. For example, when comparing a bilayer film obtained by biaxially stretching and laminating a PTFE sheet having a thickness of 200 μm and a single layer film obtained by biaxially stretching a PTFE sheet having a thickness of 400 μm at the same magnification, However, the two-layer film has higher strength. The reason is as follows. For example, in the case of obtaining a PTFE sheet before stretching by rolling a paste compact, the pressure applied to the paste compact to obtain a PTFE sheet having a thickness of 200 μm is obtained to obtain a PTFE sheet having a thickness of 400 μm. Greater than the pressure applied to the paste compact. When the pressure applied to the paste compact is large, the binding force acting between the PTFEs increases, and the strength of the finally obtained PTFE porous membrane also increases. The same applies when not rolling, for example, when the paste is extruded into a sheet by a T-die. That is, in order to obtain a high-strength PTFE porous membrane, not only the stretching ratio but also the pressure history of the PTFE sheet before stretching is extremely important.
　本発明の防水通音膜では、これを利用し、高い延伸倍率で延伸した、平均孔径および面密度が小さいＰＴＦＥ多孔質膜（多孔質層）を複数層積層および一体化することで、通音性および防水性を高いレベルで両立させた防水通音膜としている。ここで、ＰＴＦＥ多孔質膜を構成するＰＴＦＥの平均分子量が所定の値以上であることが重要であり、平均分子量が小さいＰＴＦＥを用いた場合、本発明の効果は得られない。 In the waterproof sound-permeable membrane of the present invention, by utilizing this, a PTFE porous membrane (porous layer) stretched at a high stretch ratio and having a small average pore diameter and surface density is laminated and integrated into a plurality of layers. It is a waterproof sound-permeable membrane that has both high performance and waterproofness. Here, it is important that the average molecular weight of PTFE constituting the PTFE porous membrane is not less than a predetermined value. When PTFE having a small average molecular weight is used, the effect of the present invention cannot be obtained.
　ところで、ＰＴＦＥの分子量が高くなるほど、得られた多孔質膜の通気性が低下する（圧力損失が増大する）。その理由はよくわかっていないが、ＰＴＦＥの分子量の増大により、得られた多孔質膜の網目構造が通気性を低下させる方向に変化するためであると考えられる。このため、特開平7-292144号公報に開示されているような、通気性の高さが非常に重要となる高性能エアフィルター用多孔質膜に対しては、高分子量のＰＴＦＥを適用できない。高分子量のＰＴＦＥを無理に適用した場合、延伸倍率を上げることで多孔質膜の気孔率を増加させれば、当該膜の通気性が少しは上昇すると考えられるが、今度は、特開平7-292144号公報にも記載されているように（段落0010参照）、ピンホール発生の可能性が増大してしまう。 Incidentally, the higher the molecular weight of PTFE, the lower the air permeability of the obtained porous membrane (the pressure loss increases). The reason for this is not well understood, but it is thought that this is because the network structure of the obtained porous membrane changes in the direction of decreasing the air permeability due to the increase in the molecular weight of PTFE. For this reason, high molecular weight PTFE cannot be applied to a porous membrane for a high performance air filter in which high air permeability is very important as disclosed in JP-A-7-292144. When the high molecular weight PTFE is forcibly applied, increasing the porosity of the porous membrane by increasing the draw ratio is considered to increase the air permeability of the membrane slightly. As described in Japanese Patent No. 292144 (see paragraph 0010), the possibility of occurrence of pinholes increases.
　これに対して本発明は、高い通気性を必要としない防水通音膜に関するものであり（音声は、膜自体の振動により伝播される）、エアフィルタには適していない高分子量ＰＴＦＥを、あえて使用することでなされたものである。 On the other hand, the present invention relates to a waterproof sound-permeable membrane that does not require high breathability (sound is propagated by vibration of the membrane itself) and dares high molecular weight PTFE not suitable for an air filter. It was made by using.
本発明の実施形態に係る防水通音膜の製造方法を示す工程説明図である。It is process explanatory drawing which shows the manufacturing method of the waterproof sound-permeable membrane which concerns on embodiment of this invention. 図１Ａに続く工程説明図である。It is process explanatory drawing following FIG. 1A. 本発明の防水通音膜の一例を示す斜視図である。It is a perspective view which shows an example of the waterproof sound-permeable membrane of this invention. 図２Ａに示す防水通音膜の断面図である。It is sectional drawing of the waterproof sound-permeable membrane shown to FIG. 2A. 本発明の防水通音膜の別の一例を示す斜視図である。It is a perspective view which shows another example of the waterproof sound-permeable membrane of this invention. 防水通音膜が適用された携帯電話の一例を示す正面図である。It is a front view which shows an example of the mobile telephone to which the waterproof sound-permeable membrane was applied. 防水通音膜が適用された携帯電話の一例を示す背面図である。It is a rear view which shows an example of the mobile telephone to which the waterproof sound-permeable membrane was applied. ２枚のセパレータの間に保持された防水通音膜の一例を示す断面図である。It is sectional drawing which shows an example of the waterproof sound-permeable membrane hold | maintained between two separators. 図５Ａに示す防水通音膜の平面図である。It is a top view of the waterproof sound-permeable membrane shown in FIG. 5A. セパレータおよび防水通音膜の別の一例を示す平面図である。It is a top view which shows another example of a separator and a waterproof sound-permeable membrane. セパレータおよび防水通音膜のまた別の一例を示す平面図である。It is a top view which shows another example of a separator and a waterproof sound-permeable membrane. セパレータおよび防水通音膜のさらに別の一例を示す平面図である。It is a top view which shows another example of a separator and a waterproof sound-permeable membrane.
　以下、本発明の実施形態について図面を参照しながら説明する。図１Ａは、本発明の実施形態にかかる防水通音膜の製造方法を示す工程説明図である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1A is a process explanatory diagram illustrating a method for manufacturing a waterproof sound-permeable membrane according to an embodiment of the present invention.
　（１）ペースト準備工程
　最初に、ＰＴＦＥ微粉末２０と加工助剤２１（液状潤滑剤）とを所定割合で含む混合物を十分に混練し、押出成形用のペースト２２を準備する。ＰＴＦＥ微粉末２０を構成するＰＴＦＥの平均分子量は、標準比重法により算出した数平均分子量にして５．０×１０7以上であり、７．０×１０7以上が好ましく、９．０×１０7以上がより好ましく、１．０×１０8以上がさらに好ましく、１．１×１０8以上が最も好ましい。平均分子量の上限は特に限定されないが、上記数平均分子量にして、例えば２．０×１０8である。平均分子量に関するこの規定を満たす限り、ＰＴＦＥ微粉末２０は、乳化重合法のような公知の方法によって製造された市販品でよい。ＰＴＦＥ微粉末２０の平均粒径は、例えば０．２～１．０μｍである。加工助剤２１には、ナフサや流動パラフィンなどの有機溶剤を用いることができる。ＰＴＦＥ微粉末２０と加工助剤２１との混合比率は、１００質量部のＰＴＦＥ微粉末２０に対して、例えば、加工助剤２１が１５～３０質量部である。 (1) Paste preparation step First, a mixture 22 containing PTFE fine powder 20 and processing aid 21 (liquid lubricant) in a predetermined ratio is sufficiently kneaded to prepare a paste 22 for extrusion molding. The average molecular weight of PTFE constituting the PTFE fine powder 20 is 5.0 × 10 7 or more in terms of the number average molecular weight calculated by the standard specific gravity method, preferably 7.0 × 10 7 or more, and 9.0 × 10 7. The above is more preferable, 1.0 × 10 8 or more is more preferable, and 1.1 × 10 8 or more is most preferable. The upper limit of the average molecular weight is not particularly limited, but is, for example, 2.0 × 10 8 in terms of the number average molecular weight. As long as this rule regarding the average molecular weight is satisfied, the PTFE fine powder 20 may be a commercially available product manufactured by a known method such as an emulsion polymerization method. The average particle diameter of the PTFE fine powder 20 is, for example, 0.2 to 1.0 μm. As the processing aid 21, an organic solvent such as naphtha or liquid paraffin can be used. The mixing ratio of the PTFE fine powder 20 and the processing aid 21 is, for example, 15 to 30 parts by mass of the processing aid 21 with respect to 100 parts by mass of the PTFE fine powder 20.
　（２）予備成形工程
　次に、ＰＴＦＥ微粉末と加工助剤とを含むペースト２２を円筒状に予備成形する。予備成形は、ペースト２２に１０～３０ｋｇ／ｃｍ2程度の圧力を加えて行うとよい。十分な圧力を加えることにより、ペースト内部のボイド（空隙）が圧縮され、物性が安定化する。 (2) Pre-forming step Next, the paste 22 containing the PTFE fine powder and the processing aid is pre-formed into a cylindrical shape. The preforming may be performed by applying a pressure of about 10 to 30 kg / cm 2 to the paste 22. By applying a sufficient pressure, voids (voids) inside the paste are compressed and the physical properties are stabilized.
　（３）押出成形工程
　次に、予備成形されたペースト２２を公知の押出法により成形し、シート状またはロッド状の成形体２３ａを得る。 (3) Extrusion molding step Next, the preformed paste 22 is molded by a known extrusion method to obtain a sheet-shaped or rod-shaped molded body 23a.
　シート状の成形体２３ａを得る場合、当該成形体の引張強度が、好ましくは１ＭＰａ以上、より好ましくは１．３ＭＰａ以上となるように成形を行うことが好ましく、このとき、最終的に得られるＰＴＦＥ多孔質膜１の強度がより高く、平均孔径がより小さくなる。 When obtaining the sheet-shaped molded body 23a, it is preferable to perform molding so that the tensile strength of the molded body is preferably 1 MPa or more, more preferably 1.3 MPa or more. At this time, PTFE finally obtained The strength of the porous membrane 1 is higher and the average pore size is smaller.
　（４）圧延工程
　次に、シート状またはロッド状の成形体２３ａを圧延し、帯状のＰＴＦＥシート２３ｂを得る。この時点でのＰＴＦＥシート２３ｂの厚さは、例えば、０．１～１．０ｍｍである。圧延工程においては、シート状またはロッド状の成形体２３ａに十分な圧力を加えるとよい。具体的には、（圧延後の面積）／（圧延前の面積）で表される引き延ばし率が３～３０（あるいは５～２０）となるように、圧延ロール２５，２５の隙間を調整するとよい。これによりＰＴＦＥの粒子間に働く結着力が強くなり、最終的に得られるＰＴＦＥ多孔質膜の強度が向上する。 (4) Rolling Step Next, the sheet-shaped or rod-shaped formed body 23a is rolled to obtain a strip-shaped PTFE sheet 23b. The thickness of the PTFE sheet 23b at this time is, for example, 0.1 to 1.0 mm. In the rolling step, sufficient pressure may be applied to the sheet-shaped or rod-shaped molded body 23a. Specifically, the gap between the rolling rolls 25 and 25 may be adjusted so that the stretching ratio represented by (area after rolling) / (area before rolling) is 3 to 30 (or 5 to 20). . As a result, the binding force acting between the PTFE particles is increased, and the strength of the finally obtained PTFE porous membrane is improved.
　なお、圧延前の成形体２３ａがシート状である場合には、圧延工程を省略することも可能である。すなわち、押出法によってシート状に成形された成形体２３ａを乾燥させ、圧延を行うことなく延伸してもよい。 In addition, when the formed body 23a before rolling is a sheet, the rolling step can be omitted. That is, you may dry the molded object 23a shape | molded by the extrusion method in the sheet form, and without rolling.
　（５）乾燥工程
　次に、圧延されたＰＴＦＥシート２３ｂを乾燥機２６内で乾燥させる。乾燥機２６の雰囲気温度は、ＰＴＦＥの融点未満の温度、例えば、５０～２００℃に保たれる。乾燥工程により加工助剤が揮発し、加工助剤の含有量が十分に減じられたＰＴＦＥシート２３ｃが得られる。 (5) Drying step Next, the rolled PTFE sheet 23 b is dried in the dryer 26. The atmospheric temperature of the dryer 26 is maintained at a temperature lower than the melting point of PTFE, for example, 50 to 200 ° C. The processing aid is volatilized by the drying step, and the PTFE sheet 23c in which the content of the processing aid is sufficiently reduced is obtained.
　（６）第１の延伸工程
　次に、図１Ｂに示すように、乾燥させたＰＴＦＥシート２３ｃを長手方向（ＭＤ）に延伸する。長手方向の延伸倍率は、例えば３～３０倍であり、５～２０倍としてもよい。長手方向の延伸倍率をこの程度まで高くすることにより、ＰＴＦＥ分子の配向を十分に促進でき、ひいてはＰＴＦＥ多孔質膜の強度を高めることができる。第１の延伸工程は、ＰＴＦＥシート２３ｃの柔軟性が十分に発揮される温度であって、ＰＴＦＥの融点未満の温度、例えば、１５０～３００℃の雰囲気温度で行うことができる。図１Ａに示す乾燥工程で用いた乾燥機２６内で第１の延伸工程を行ってもよい。 (6) First Stretching Step Next, as shown in FIG. 1B, the dried PTFE sheet 23c is stretched in the longitudinal direction (MD). The draw ratio in the longitudinal direction is, for example, 3 to 30 times, and may be 5 to 20 times. By increasing the stretching ratio in the longitudinal direction to this extent, the orientation of PTFE molecules can be sufficiently promoted, and consequently the strength of the PTFE porous membrane can be increased. The first stretching step can be performed at a temperature at which the flexibility of the PTFE sheet 23c is sufficiently exhibited, and a temperature lower than the melting point of PTFE, for example, an ambient temperature of 150 to 300 ° C. You may perform a 1st extending | stretching process within the dryer 26 used at the drying process shown to FIG. 1A.
　（７）重ね合わせ工程
　次に、長手方向に延伸された２枚のＰＴＦＥシート２３ｄ，２３ｄを重ね合わせる。重ね合わせは、一方のＰＴＦＥシート２３ｄの搬送経路と、他方のＰＴＦＥシート２３ｄの搬送経路とを合流させる形で行うとよい。そのようにすれば、２枚のＰＴＦＥシート２３ｄ，２３ｄの長手方向を揃えて重ね合わせを行うことになるので、重ね合わせるべきＰＴＦＥシート２３ｄを裁断する必要がなく、生産性に優れる。ここで、ＰＴＦＥシート２３ｄの重ね合わせ枚数は、工程が煩雑にならない範囲内で定めることができる。 (7) Superposition process Next, the two PTFE sheets 23d and 23d stretched in the longitudinal direction are superposed. The superposition may be performed in such a manner that the conveyance path of one PTFE sheet 23d and the conveyance path of the other PTFE sheet 23d are merged. By doing so, since the two PTFE sheets 23d, 23d are aligned in the longitudinal direction, it is not necessary to cut the PTFE sheet 23d to be overlapped, and the productivity is excellent. Here, the number of overlapping PTFE sheets 23d can be determined within a range in which the process is not complicated.
　上述したように、ＰＴＦＥ多孔質膜の強度は、延伸前にＰＴＦＥシートが受けた加圧履歴と延伸倍率とによって変化する。より高い圧力で圧延されたＰＴＦＥシート２３ｂを得るには、圧延工程において、圧延ロール２５，２５の隙間を狭くするとよい。圧延ロール２５，２５の隙間を狭くすると、得られるＰＴＦＥシート２３ｂの厚さが小さくなるが、この場合、最終的に必要な面密度が確保されるように、重ね合わせ工程における重ね合わせ枚数を増やせばよい。また、延伸倍率の上昇に対しても、重ね合わせ枚数の増加で対応できる。具体的には、後述の実施例に示すように、３層構造や４層構造のＰＴＦＥ多孔質膜を防水通音膜に好適に使用できる。 As described above, the strength of the PTFE porous membrane varies depending on the pressurization history and stretch ratio received by the PTFE sheet before stretching. In order to obtain the PTFE sheet 23b rolled at a higher pressure, the gap between the rolling rolls 25 and 25 may be narrowed in the rolling process. If the gap between the rolling rolls 25 is narrowed, the thickness of the obtained PTFE sheet 23b is reduced. In this case, however, the number of overlapping sheets in the overlapping process can be increased so that the required surface density is finally secured. That's fine. Further, an increase in the draw ratio can be handled by increasing the number of overlapping sheets. Specifically, as shown in the examples described later, a PTFE porous membrane having a three-layer structure or a four-layer structure can be suitably used for a waterproof sound-permeable membrane.
　（８）第２の延伸工程
　次に、重ね合わされた２枚のＰＴＦＥシート２３ｄ，２３ｄを、その重ね合わせ状態を維持しつつ、長手方向と直交する幅方向（ＴＤ）に延伸する。幅方向の延伸倍率は、例えば３～１００倍であり、２０～８０倍としてもよい。幅方向の延伸倍率をこの程度まで高くすることにより、長手方向の高い延伸倍率とあいまって、ＰＴＦＥ多孔質膜のさらなる高強度化を図ることができる。幅方向の延伸工程は、ＰＴＦＥの融点未満の温度、例えば、５０～３００℃の雰囲気温度で、公知のテンター法により行うことができる。 (8) Second Stretching Step Next, the two superimposed PTFE sheets 23d and 23d are stretched in the width direction (TD) orthogonal to the longitudinal direction while maintaining the superposed state. The draw ratio in the width direction is, for example, 3 to 100 times, and may be 20 to 80 times. By increasing the stretching ratio in the width direction to this level, the PTFE porous membrane can be further strengthened in combination with the high stretching ratio in the longitudinal direction. The stretching process in the width direction can be performed by a known tenter method at a temperature lower than the melting point of PTFE, for example, an ambient temperature of 50 to 300 ° C.
　（９）焼成工程
　最後に、２軸方向に延伸された２枚のＰＴＦＥシート２３ｅ，２３ｅをＰＴＦＥの融点以上の温度、例えば、３５０～５００℃（炉２７の雰囲気温度）で焼成する。焼成工程を行うことにより、ＰＴＦＥのマトリクス間に働く結着力に基づき、２枚のＰＴＦＥシート２３ｅ，２３ｅが両者の境界面の全体にわたって一体化する。これにより、防水通音膜に用いられるＰＴＦＥ多孔質膜１が得られる。この焼成工程は、２枚のＰＴＦＥシート２３ｅ，２３ｅを加圧しながら行ってもよいし、プレス型または熱ロールに接触させることによって行ってもよい。 (9) Firing step Finally, the two PTFE sheets 23e and 23e stretched in the biaxial direction are fired at a temperature equal to or higher than the melting point of PTFE, for example, 350 to 500 ° C. (atmosphere temperature in the furnace 27). By performing the firing step, the two PTFE sheets 23e and 23e are integrated over the entire boundary surface based on the binding force acting between the PTFE matrices. Thereby, the PTFE porous membrane 1 used for a waterproof sound-permeable membrane is obtained. This firing step may be performed while pressing the two PTFE sheets 23e and 23e, or may be performed by bringing them into contact with a press die or a hot roll.
　第１および第２の延伸工程ならびに圧延工程は、焼成工程後におけるＰＴＦＥシート（多孔質層）２３ｅ，２３ｅの平均孔径が１μｍ以下となるように行う。また、第１および第２の延伸工程、圧延工程ならびに重ね合わせ工程は、焼成工程後に得られるＰＴＦＥ多孔質膜１の面密度が１～１０ｇ／ｍ2となり、引張強度が１０～１００ＭＰａとなり、突き刺し強度を面密度で除した値が２５～５０ｋＰａ・ｍ2／ｇとなるように行う。 The first and second stretching steps and the rolling step are performed so that the average pore diameter of the PTFE sheets (porous layers) 23e and 23e after the firing step is 1 μm or less. Further, in the first and second stretching steps, the rolling step and the overlapping step, the PTFE porous membrane 1 obtained after the firing step has an area density of 1 to 10 g / m 2 and a tensile strength of 10 to 100 MPa. The value obtained by dividing the strength by the surface density is 25 to 50 kPa · m 2 / g.
　本実施形態では、ＰＴＦＥの融点以下の温度にて高延伸倍率で延伸を行うことで平均孔径を小さくかつマトリクス強度を向上させた延伸膜を、複数枚積層する。これにより、同じ面密度で単層の膜よりも高い防水性を示す防水通音膜を提供できる。ここで、高延伸倍率の延伸とは、第１および第２の延伸工程ならびに圧延工程を積算して、面積延伸倍率にして５００～１００００倍、好ましくは１０００～１００００倍、より好ましくは２０００～１００００倍の延伸である。 In this embodiment, a plurality of stretched films having a small average pore diameter and improved matrix strength are laminated by stretching at a high stretch ratio at a temperature not higher than the melting point of PTFE. Thereby, it is possible to provide a waterproof sound-permeable membrane having the same surface density and higher waterproofness than a single layer membrane. Here, the stretching at a high stretching ratio means that the first and second stretching steps and the rolling step are integrated to obtain an area stretching ratio of 500 to 10,000 times, preferably 1000 to 10,000 times, more preferably 2000 to 10,000. Double stretching.
　図１Ａおよび図１Ｂに示す製造方法によれば、第１の延伸工程と第２の延伸工程との間に重ね合わせ工程を挟んでいるが、第１の延伸工程と第２の延伸工程とを連続的に行うようにしてもよい。すなわち、未延伸のＰＴＦＥシートを複数枚重ね合わせた後、重ね合わされたＰＴＦＥシートをテンター法のような公知の延伸方法により２軸延伸してもよい。 According to the manufacturing method shown in FIG. 1A and FIG. 1B, the overlapping process is sandwiched between the first stretching process and the second stretching process, but the first stretching process and the second stretching process are performed. You may make it carry out continuously. That is, after overlapping a plurality of unstretched PTFE sheets, the stacked PTFE sheets may be biaxially stretched by a known stretching method such as a tenter method.
　ただし、重ね合わせ工程の後で２軸延伸工程を行う場合、多孔質構造が不均一になる可能性がある。なぜなら、重ね合わされたＰＴＦＥシートの界面近傍の部分と、界面から離れた部分とで張力のかかり方が相違するからである。多孔質構造が不均一になると、通音性に影響がでる。これに対して、本実施形態によれば、長手方向の延伸で微孔を形成した後に、重ね合わせおよび幅方向の延伸を行うため、従来の単層の場合と比較しても遜色のない良質な多孔質構造が形成される。また、長手方向に延伸されたＰＴＦＥシートのハンドリング性は、未延伸のＰＴＦＥシートのハンドリング性よりも高い。したがって、本実施形態によれば、正確に重ね合わせ工程を行うことができるとともに、シート間に空気泡が挟まれるような問題も生じにくい。また、未延伸のシートを重ね合わせても容易に接着しないが、長手方向に延伸した後のシートは容易かつ均一に接着できる。 However, when the biaxial stretching process is performed after the superimposing process, the porous structure may be non-uniform. This is because the tension is applied differently in the vicinity of the interface between the overlapped PTFE sheets and the part away from the interface. If the porous structure becomes non-uniform, sound transmission will be affected. On the other hand, according to this embodiment, after forming the micropores by stretching in the longitudinal direction, superposition and stretching in the width direction are performed, so that the quality is comparable to that of a conventional single layer. A porous structure is formed. Moreover, the handling property of the PTFE sheet stretched in the longitudinal direction is higher than the handling property of the unstretched PTFE sheet. Therefore, according to the present embodiment, it is possible to perform the overlaying process accurately, and it is difficult to cause a problem that air bubbles are sandwiched between sheets. Further, even if unstretched sheets are stacked, they are not easily bonded, but the sheet after being stretched in the longitudinal direction can be easily and uniformly bonded.
　また、本実施形態のように、長手方向の延伸工程と、幅方向の延伸工程との間に、重ね合わせ工程を挟むことにより、長手方向の延伸倍率が互いに相違する２つの層を有するＰＴＦＥ多孔質膜を製造できる。このような特殊なＰＴＦＥ多孔質膜は、面密度および膜厚の微調整が必要となる製品（防水通音膜）に有効である。 Further, as in the present embodiment, a PTFE porous material having two layers having different stretching ratios in the longitudinal direction by sandwiching an overlapping process between the stretching process in the longitudinal direction and the stretching process in the width direction. A membrane can be produced. Such a special PTFE porous membrane is effective for a product (waterproof sound-permeable membrane) that requires fine adjustment of the surface density and the film thickness.
　また、予め２軸延伸された複数枚のＰＴＦＥシートを重ね合わせ、焼成により一体化するようにしてもよい。ただし、現実の生産過程において、幅方向への延伸を行った後のＰＴＦＥシートの面積は非常に大きくなるので、当該順序によれば、重ね合わせが困難となる可能性がある。 Also, a plurality of PTFE sheets biaxially stretched in advance may be superposed and integrated by firing. However, in the actual production process, the area of the PTFE sheet after being stretched in the width direction becomes very large. Therefore, according to the order, it may be difficult to superimpose.
　これに対し、幅方向の延伸の前に重ね合わせを行う場合には、ＰＴＦＥシートの幅が狭いので重ね合わせが容易であり、重ね合わせ時にＰＴＦＥシートにシワが生じたり、亀裂が入ったりするなどの不具合が生じにくく、ひいては重ね合わせ工程の追加に伴う歩留まりの低下を抑制することが可能となる。図１Ｂに示すように、本実施形態によれば、重ね合わせの前に長手方向の延伸を行っているが、ＰＴＦＥシートの長手方向は、通常、圧延方向や搬送方向に沿う方向であるから、長手方向の面積拡大はＰＴＦＥシートのハンドリング容易性に大した影響を及ぼさず、重ね合わせの困難性を高める要因となりにくい。 On the other hand, when overlapping is performed before stretching in the width direction, since the PTFE sheet is narrow, it is easy to overlap, and the PTFE sheet is wrinkled or cracked at the time of overlapping. Thus, it is possible to suppress a decrease in yield due to the addition of the overlaying process. As shown in FIG. 1B, according to the present embodiment, the longitudinal direction is stretched before superposition, but the longitudinal direction of the PTFE sheet is usually a direction along the rolling direction and the conveying direction. Expansion of the area in the longitudinal direction does not significantly affect the ease of handling of the PTFE sheet, and is unlikely to increase the difficulty of overlaying.
　本発明の製造方法では、上述した各工程以外の工程を、必要に応じ、任意の時点で実施してもよく、当該工程は、第１および第２の延伸工程以外の延伸工程であってもよい。 In the production method of the present invention, steps other than the above-described steps may be performed at any time as necessary, and the steps may be stretching steps other than the first and second stretching steps. Good.
　以上に説明した方法により、図２Ａおよび図２Ｂに示す防水通音膜１０を製造することができる。 The waterproof sound-permeable membrane 10 shown in FIGS. 2A and 2B can be manufactured by the method described above.
　図２Ａに示す防水通音膜１０は、円板状のＰＴＦＥ多孔質膜１で作られている。図２Ｂに示すように、防水通音膜１０としてのＰＴＦＥ多孔質膜１は、第１多孔質層１ａと、第２多孔質層１ｂとを備える。第２多孔質層１ｂは、ＰＴＦＥのマトリクス間に働く結着力に基づいて第１多孔質層１ａに積層および一体化されている。図１Ａおよび図１Ｂで説明した製造方法によれば、第１多孔質層１ａと第２多孔質層１ｂとは、実質的に同一のマトリクス構造を有したものとなる。言い換えれば、第１多孔質層１ａの延伸方向と第２多孔質層１ｂの延伸方向とが一致するとともに、延伸倍率が各延伸方向に関して等しくなる。また、第１多孔質層１ａの厚さと第２多孔質層１ｂの厚さも同一となる。 The waterproof sound-permeable membrane 10 shown in FIG. 2A is made of a disk-shaped PTFE porous membrane 1. As shown in FIG. 2B, the PTFE porous membrane 1 as the waterproof sound-permeable membrane 10 includes a first porous layer 1a and a second porous layer 1b. The second porous layer 1b is laminated and integrated with the first porous layer 1a based on the binding force acting between the PTFE matrices. According to the manufacturing method described in FIGS. 1A and 1B, the first porous layer 1a and the second porous layer 1b have substantially the same matrix structure. In other words, the stretching direction of the first porous layer 1a matches the stretching direction of the second porous layer 1b, and the stretching ratio is equal in each stretching direction. Moreover, the thickness of the 1st porous layer 1a and the thickness of the 2nd porous layer 1b are also the same.
　防水通音膜１０の面密度は（複数層の合計で）１～１０ｇ／ｍ2である。面密度がこのような範囲内にある防水通音膜１０は、物理的強度が十分であるとともに、音響透過損失が小さく、通音性に優れる。防水通音膜１０の面密度は、２～１０ｇ／ｍ2が好ましく、２～７ｇ／ｍ2がより好ましい。 The surface density of the waterproof sound-permeable membrane 10 is 1 to 10 g / m 2 (total of a plurality of layers). The waterproof sound-permeable membrane 10 having an areal density in such a range has sufficient physical strength, small acoustic transmission loss, and excellent sound permeability. The surface density of the waterproof sound-permeable membrane 10 is preferably 2 to 10 g / m 2 and more preferably 2 to 7 g / m 2 .
　第１多孔質層１ａおよび第２多孔質層１ｂから選ばれる少なくとも１つの層の平均孔径は、１μｍ以下である。防水性向上のためには、両方の層の平均孔径が１μｍ以下であることが好ましい。防水通音膜１０を構成する多孔質層１ａ，１ｂの平均孔径が１μｍ以下であることによって、防水性が高い防水通音膜１０となる。多孔質層１ａ，１ｂの平均孔径は、０．７μｍ以下が好ましく、０．５μｍ以下がより好ましい。多孔質層１ａ，１ｂの平均孔径が小さくなることによって防水通音膜１０の通気性は低下するが、音声は膜自体の振動により伝播されるため、膜の通気性は通音性にそれほど影響を与えない。平均孔径の下限は特に限定されないが、例えば０．１μｍである。 The average pore diameter of at least one layer selected from the first porous layer 1a and the second porous layer 1b is 1 μm or less. In order to improve waterproofness, the average pore diameter of both layers is preferably 1 μm or less. When the average pore diameter of the porous layers 1 a and 1 b constituting the waterproof sound-permeable membrane 10 is 1 μm or less, the waterproof sound-permeable membrane 10 having high waterproofness is obtained. The average pore diameter of the porous layers 1a and 1b is preferably 0.7 μm or less, and more preferably 0.5 μm or less. Although the air permeability of the waterproof sound-permeable membrane 10 is reduced by decreasing the average pore diameter of the porous layers 1a and 1b, since sound is propagated by vibration of the membrane itself, the air permeability of the membrane has a great influence on the sound permeability. Not give. Although the minimum of an average hole diameter is not specifically limited, For example, it is 0.1 micrometer.
　なお、平均孔径の測定方法は、ＡＳＴＭ　Ｆ３１６－８６に記載されている測定法が一般的に普及しており、自動化された測定装置が市販されている（例えば、米国Porous Material Inc.より入手可能なPerm-Porometer）。この方式は、既知の表面張力を持つ液体に浸漬したＰＴＦＥ多孔質膜をホルダに固定し、一方から加圧することによって膜から液体を追い出し、その圧力から平均孔径を求めるものである。この方式は簡便かつ再現性が高いだけでなく、測定装置を完全に自動化できるという点で優れている。 As the average pore diameter measurement method, the measurement method described in ASTM F316-86 is generally widespread, and an automated measurement device is commercially available (for example, available from Porous Material Inc., USA). Perm-Porometer). In this method, a PTFE porous membrane immersed in a liquid having a known surface tension is fixed to a holder, and the liquid is expelled from the membrane by applying pressure from one side, and the average pore diameter is obtained from the pressure. This method is not only simple and high in reproducibility, but also excellent in that the measuring apparatus can be completely automated.
　第１多孔質層１ａおよび第２多孔質層１ｂの気孔率は特に限定されないが、６０～９５％が好ましく、７５～９５％がより好ましい。 The porosity of the first porous layer 1a and the second porous layer 1b is not particularly limited, but is preferably 60 to 95%, more preferably 75 to 95%.
　防水通音膜１０の引張強度は、１０～１００ＭＰａである。引張強度がこの範囲にあることによって、防水性（耐水圧特性）が高い防水通音膜１０となる。防水通音膜１０の引張強度は２０～７５ＭＰａが好ましい。なお、防水通音膜１０の引張強度は、本来、高ければ高いほど膜の耐水圧性にとって好ましいが、上記面密度の範囲、即ち防水通音膜１０の通音性を考慮すると、上記範囲となる。また、防水通音膜１０の引張強度が方向により異なる場合、最も低くなる方向への引張強度が１０～１００ＭＰａであればよい。 The tensile strength of the waterproof sound-permeable membrane 10 is 10 to 100 MPa. When the tensile strength is in this range, the waterproof sound-permeable membrane 10 having high waterproofness (water pressure resistance) is obtained. The tensile strength of the waterproof sound-permeable membrane 10 is preferably 20 to 75 MPa. Note that the tensile strength of the waterproof sound-permeable membrane 10 is inherently higher for the water pressure resistance of the membrane, but it is within the above range in consideration of the above surface density range, that is, the sound-permeable property of the waterproof sound-permeable membrane 10. . Further, when the tensile strength of the waterproof sound-permeable membrane 10 varies depending on the direction, the tensile strength in the lowest direction may be 10 to 100 MPa.
　防水通音膜１０の突き刺し強度は、面密度で除した値にして２５～５０ｋＰａ・ｍ2／ｇである。突き刺し強度がこの範囲にあることによって、防水性が高い防水通音膜１０となる。なお、防水通音膜１０の突き刺し強度は、本来、高ければ高いほど膜の防水性にとって好ましいが、上記面密度の範囲、即ち防水通音膜１０の通音性を考慮すると、上記範囲となる。また、面密度で除した値を突き刺し強度として用いているのは、引張強度に比べて、突き刺し強度が膜の面密度に大きな影響を受けるためである。面密度で除していない突き刺し強度の値としては、例えば１００～５００ｋＰａである。 The piercing strength of the waterproof sound-permeable membrane 10 is 25 to 50 kPa · m 2 / g as a value divided by the surface density. When the puncture strength is in this range, the waterproof sound-permeable membrane 10 having high waterproofness is obtained. Note that the piercing strength of the waterproof sound-permeable membrane 10 is inherently higher for the waterproof property of the membrane, but it is in the above range in consideration of the above surface density range, that is, the sound-permeable property of the waterproof sound-permeable membrane 10. . The reason why the value divided by the surface density is used as the piercing strength is that the piercing strength is greatly influenced by the surface density of the film as compared with the tensile strength. The value of the piercing strength not divided by the surface density is, for example, 100 to 500 kPa.
　防水通音膜１０には、その防水性をさらに高めるために、含フッ素ポリマーなどの撥水剤を用いて撥水処理を行ってもよい。 The waterproof sound-permeable membrane 10 may be subjected to a water-repellent treatment using a water-repellent agent such as a fluorine-containing polymer in order to further improve the waterproof property.
　本発明の防水通音膜は、ＰＴＦＥ多孔質膜１の周縁に固着された枠を備えていてもよい。図３は、ＰＴＦＥ多孔質膜１の周縁部に、リング状の枠３が取り付けられた防水通音膜１２を示している。このように、リング状の枠３を設けた形態によれば、ＰＴＦＥ多孔質膜１を補強することができ、防水通音膜１２の取り扱いが容易となる。また、この枠３が電気製品の筐体への取付しろとなるため、防水通音膜１２の筐体への取り付け作業が容易となる。さらに、防水通音膜１２における通音部分がＰＴＦＥ多孔質膜１単体であることから、ＰＴＦＥ多孔質膜１の全面に支持体としてネットなどを貼り合わせた形態よりも、高い通音性を確保できる。 The waterproof sound-permeable membrane of the present invention may include a frame fixed to the peripheral edge of the PTFE porous membrane 1. FIG. 3 shows a waterproof sound-permeable membrane 12 in which a ring-shaped frame 3 is attached to the peripheral edge of the PTFE porous membrane 1. Thus, according to the form in which the ring-shaped frame 3 is provided, the PTFE porous membrane 1 can be reinforced, and the waterproof sound-permeable membrane 12 can be easily handled. In addition, since the frame 3 can be attached to the housing of the electrical product, it is easy to attach the waterproof sound-permeable membrane 12 to the housing. Further, since the sound-transmitting portion of the waterproof sound-permeable membrane 12 is the PTFE porous membrane 1 alone, higher sound permeability is ensured than the form in which a net or the like is bonded to the entire surface of the PTFE porous membrane 1 as a support. it can.
　枠３の材質は特に限定されないが、熱可塑性樹脂あるいは金属が好適である。熱可塑性樹脂は、例えば、ポリエチレン（ＰＥ）、ポリプロピレン（ＰＰ）などのポリオレフィン；ポリエチレンテレフタレート（ＰＥＴ）などのポリエステル；ポリカーボネート（ＰＣ）；ポリイミド；あるいはこれらの複合材である。金属は、例えば、ステンレスやアルミニウムのような耐蝕性に優れる金属である。 The material of the frame 3 is not particularly limited, but a thermoplastic resin or metal is suitable. The thermoplastic resin is, for example, a polyolefin such as polyethylene (PE) or polypropylene (PP); a polyester such as polyethylene terephthalate (PET); a polycarbonate (PC); a polyimide; or a composite material thereof. The metal is a metal having excellent corrosion resistance, such as stainless steel or aluminum.
　リング状の枠３の厚さは、例えば５～５００μｍであり、２５～２００μｍが好ましい。また、リング幅（外径と内径の差）は０．５～２ｍｍ程度が、電気製品の筐体への取付しろとして適当である。また、リング状の枠３には、上記樹脂からなる発泡体を使用してもよい。 The thickness of the ring-shaped frame 3 is, for example, 5 to 500 μm, and preferably 25 to 200 μm. In addition, a ring width (difference between outer diameter and inner diameter) of about 0.5 to 2 mm is suitable as an allowance for mounting an electrical product on a casing. Moreover, you may use the foam which consists of the said resin for the ring-shaped frame 3. FIG.
　ＰＴＦＥ多孔質膜１と枠３との接着方法は特に限定されず、例えば、加熱溶着、超音波溶着、接着剤による接着、両面テープによる接着などの方法を適用できる。特に、両面テープによる接着が、ＰＴＦＥ多孔質膜１と枠３との接着が容易であることから好ましい。 The adhesion method between the PTFE porous membrane 1 and the frame 3 is not particularly limited, and for example, methods such as heat welding, ultrasonic welding, adhesion with an adhesive, and adhesion with a double-sided tape can be applied. In particular, adhesion with a double-sided tape is preferable because adhesion between the PTFE porous membrane 1 and the frame 3 is easy.
　図４Ａおよび図４Ｂは、防水通音膜１０が用いられた電気製品の一例を示している。図４Ａおよび図４Ｂに示す電気製品は、携帯電話５である。携帯電話５の筐体９には、スピーカー６、マイク７、ブザー８などの発音部および受音部のための開口が設けられている。それらの開口を塞ぐ形で、防水通音膜１０が内側から筐体９に取り付けられている。これにより、筐体９の内部への水や埃の侵入が阻止され、発音部および受音部が保護される。防水通音膜１０の筐体９への取り付けは、筐体９との接合部から水が浸入することのないように、例えば、両面テープを用いた貼付、熱溶着、高周波溶着、超音波溶着などの方法により行われる。 4A and 4B show an example of an electric product using the waterproof sound-permeable membrane 10. The electric product shown in FIGS. 4A and 4B is a mobile phone 5. The casing 9 of the mobile phone 5 is provided with openings for sound generation units and sound reception units such as a speaker 6, a microphone 7, and a buzzer 8. A waterproof sound-permeable membrane 10 is attached to the housing 9 from the inside so as to close these openings. Thereby, the penetration | invasion of the water and dust to the inside of the housing | casing 9 is blocked | prevented and a sound generation part and a sound receiving part are protected. The waterproof sound-permeable membrane 10 is attached to the housing 9 so that water does not enter from the joint with the housing 9, for example, using double-sided tape, thermal welding, high-frequency welding, ultrasonic welding. It is performed by such methods.
　防水通音膜１０は、携帯電話５だけでなく、音声の出力を行うための発音部および音声の入力を行うための受音部から選ばれる少なくとも１つを備えた電気製品に適用できる。具体的には、ノートパソコン、電子手帳、デジタルカメラ、携帯用オーディオのような音声機能を備えた各種電気製品に適用可能である。 The waterproof sound-permeable membrane 10 can be applied not only to the mobile phone 5 but also to an electrical product including at least one selected from a sound generation unit for outputting sound and a sound reception unit for inputting sound. Specifically, the present invention can be applied to various electric products having voice functions such as notebook computers, electronic notebooks, digital cameras, and portable audio.
　防水通音膜１０は、その表裏に両面テープを貼り付けることによって形成されたアセンブリの形で提供されうる。図５Ａに示すように、アセンブリ４０は、防水通音膜１０と、防水通音膜１０の表裏に貼り付けられた２つの両面テープ３０とを有する。両面テープ３０は、平面視でリングまたは枠の形状を有する。両面テープ３０の開口部３０ｈに防水通音膜１０が露出している。アセンブリ４０の一方の面に台紙セパレータ３４が設けられ、他方の面にタブ付きセパレータ３２が設けられている。アセンブリ４０が２枚のセパレータ３２，３４の間に保持されているので、防水通音膜１０を確実に保護できるとともに、携帯電話の筐体などの対象物への取り付け作業が容易となる。 The waterproof sound-permeable membrane 10 can be provided in the form of an assembly formed by sticking double-sided tape on the front and back. As shown in FIG. 5A, the assembly 40 includes a waterproof sound-permeable membrane 10 and two double-sided tapes 30 attached to the front and back of the waterproof sound-permeable membrane 10. The double-sided tape 30 has a ring or frame shape in plan view. The waterproof sound-permeable membrane 10 is exposed at the opening 30 h of the double-sided tape 30. A mount separator 34 is provided on one side of the assembly 40, and a tabbed separator 32 is provided on the other side. Since the assembly 40 is held between the two separators 32 and 34, the waterproof sound-permeable membrane 10 can be surely protected, and attachment work to an object such as a cellular phone housing is facilitated.
　セパレータ３２は、アセンブリ４０とともに台紙セパレータ３４から剥離されうる。図５Ｂの平面図に示すように、セパレータ３２のタブ３２ｔは、アセンブリ４０の外縁から外向きに突出するように形成されている。セパレータ３２のタブ３２ｔの部分を掴んだまま、アセンブリ４０を携帯電話の筐体などの対象物に貼り付けることができる。そして、タブ３２ｔを引き上げることにより、アセンブリ４０からセパレータ３２を容易に剥離できる。このように、防水通音膜１０に直接触れることなく、防水通音膜１０を対象物に取り付けることができるので、作業時に防水通音膜１０にダメージが及びにくい。また、対象物を傷付ける可能性も低減する。 The separator 32 can be peeled from the mount separator 34 together with the assembly 40. As shown in the plan view of FIG. 5B, the tab 32 t of the separator 32 is formed to protrude outward from the outer edge of the assembly 40. The assembly 40 can be affixed to an object such as a mobile phone casing while holding the tab 32t portion of the separator 32. The separator 32 can be easily peeled from the assembly 40 by pulling up the tab 32t. Thus, since the waterproof sound-permeable membrane 10 can be attached to an object without directly touching the waterproof sound-permeable membrane 10, the waterproof sound-permeable membrane 10 is hardly damaged during work. It also reduces the possibility of damaging the object.
　セパレータ３２，３４は、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレートなどの樹脂製であってもよいし、紙製であってもよい。台紙セパレータ３４におけるアセンブリ４０を載せる部分に、エンボス加工が施されていてもよい。台紙セパレータ３４と両面テープ３０との間の接着力（１８０°ピール接着強度）よりも、タブ付きセパレータ３２と両面テープ３０との間の接着力が強いことが好ましい。この場合、タブ付きセパレータ３２を、アセンブリ４０とともに、台紙セパレータ３４から容易に剥離できる。 The separators 32 and 34 may be made of resin such as polyethylene, polypropylene, polyethylene terephthalate, or may be made of paper. An embossing process may be performed on a portion of the mount separator 34 on which the assembly 40 is placed. It is preferable that the adhesive force between the tabbed separator 32 and the double-sided tape 30 is stronger than the adhesive force between the mount separator 34 and the double-sided tape 30 (180 ° peel adhesive strength). In this case, the tabbed separator 32 can be easily peeled from the mount separator 34 together with the assembly 40.
　通常、１つのアセンブリ４０に対して１つのタブ付きセパレータ３２が設けられる。一方で、台紙セパレータ３４は、多数個のアセンブリ４０に共有されていてもよいし、１つのアセンブリ４０に対して１つの台紙セパレータ３４が設けられていてもよい。後者の製品は、タブ付きセパレータ３２をアセンブリ４０の上に載せた後、タブ付きセパレータ３２よりも大きく台紙セパレータ３４を打ち抜くことによって得られる。 Usually, one tabbed separator 32 is provided for one assembly 40. On the other hand, the mount separator 34 may be shared by many assemblies 40, and one mount separator 34 may be provided for one assembly 40. The latter product is obtained by placing the tabbed separator 32 on the assembly 40 and then punching the backing separator 34 larger than the tabbed separator 32.
　アセンブリ４０およびタブ付きセパレータ３２の形状は特に限定されない。図６Ａに示すように、アセンブリ４０が円形であってもよい。また、図６Ｂに示すように、アセンブリ４０の全周に渡って円形のタブ３２ｔが形成されていてもよい。また、図６Ｃに示すように、アセンブリ４０が矩形であり、平面視でタブ３２ｔがアセンブリ４０を取り囲む枠の形状を有していてもよい。 The shape of the assembly 40 and the tabbed separator 32 is not particularly limited. As shown in FIG. 6A, the assembly 40 may be circular. Further, as shown in FIG. 6B, a circular tab 32t may be formed over the entire circumference of the assembly 40. Further, as shown in FIG. 6C, the assembly 40 may be rectangular, and the tab 32t may have a frame shape surrounding the assembly 40 in plan view.
　以下、実施例により本発明をさらに具体的に説明する。本発明は、以下の実施例に限定されない。 Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.
　最初に、標準比重法によるＰＴＦＥの数平均分子量の算出方法、および作製したＰＴＦＥ多孔質膜の諸特性の評価方法を説明する。 First, a method for calculating the number average molecular weight of PTFE by the standard specific gravity method and a method for evaluating various properties of the produced porous PTFE membrane will be described.
　［標準比重法によるＰＴＦＥの数平均分子量の算出］
　ＪＩＳ　Ｋ６９３５－２に準拠して求めたＰＴＦＥの標準比重（ＳＳＧ）を、以下の式（１）に代入することにより、ＰＴＦＥの数平均分子量Ｍｎを算出した。なお、式（１）は、ふっ素樹脂ハンドブック（里川孝臣編、日刊工業新聞社、１９９０年発行）３６頁に記載されている。
　　ＳＳＧ＝－０．０５７９Ｍｎ＋２．６１１３　　　　（１） [Calculation of number average molecular weight of PTFE by standard specific gravity method]
The number average molecular weight Mn of PTFE was calculated by substituting the standard specific gravity (SSG) of PTFE obtained according to JIS K6935-2 into the following formula (1). Formula (1) is described in page 36 of a fluororesin handbook (Takaomi Satokawa, published by Nikkan Kogyo Shimbun, 1990).
SSG = −0.0579Mn + 2.6113 (1)
　［平均孔径］
　ＰＴＦＥ多孔質膜を構成する各多孔質層の平均孔径は、上述したように、Porous Material Inc.製Perm-Porometerを用い、ＡＳＴＭ　Ｆ３１６－８６に準拠して求めた。測定には、フッ素系溶媒（スリーエム社製、ＦＣ－４０、表面張力１６ｍＮ／ｍ）を用いた。 [Average pore size]
As described above, the average pore diameter of each porous layer constituting the PTFE porous membrane was determined according to ASTM F316-86 using a Perm-Porometer manufactured by Porous Material Inc. For the measurement, a fluorinated solvent (manufactured by 3M, FC-40, surface tension 16 mN / m) was used.
　［面密度］
　ＰＴＦＥ多孔質膜の面密度は、φ４７ｍｍのポンチで多孔質膜を打ち抜いた後、打ち抜いた部分の質量を測定し、１ｍ2あたりの質量に換算して求めた。 [Area density]
The surface density of the PTFE porous membrane was determined by measuring the mass of the punched portion after punching the porous membrane with a φ47 mm punch and converting it to a mass per 1 m 2 .
　［引張強度］
　ＰＴＦＥ多孔質膜の引張強度は、ＪＩＳ　Ｋ７１１３に記載されている２号形試験片の形状に多孔質膜を打ち抜いた後、得られた試験片を引張試験機（エー・アンド・ディー社製、テンシロン万能試験機MODEL:RTC-1310A-PL）により、以下の条件で引張試験を行って求めた。引張強度は、ＰＴＦＥ多孔質膜の長手方向（ＭＤ）および幅方向（ＴＤ）のそれぞれに対して測定した。
　チャック間距離：９５ｍｍ
　引張速度：２００ｍｍ／分
　測定温度：２５℃ [Tensile strength]
The tensile strength of the PTFE porous membrane was determined by punching the porous membrane into the shape of No. 2 type test piece described in JIS K7113, and then using the tensile tester (manufactured by A & D Corporation, Tensylon universal testing machine MODEL: RTC-1310A-PL) was obtained by performing a tensile test under the following conditions. The tensile strength was measured with respect to each of the longitudinal direction (MD) and the width direction (TD) of the PTFE porous membrane.
Distance between chucks: 95mm
Tensile speed: 200 mm / min Measurement temperature: 25 ° C.
　引張強度は、引張試験によってＰＴＦＥ多孔質膜が破断したときの最大負荷加重（Ｎ）を、ＰＴＦＥ多孔質膜の引張試験前の断面積（ｍｍ2）で除した値とした。なお、試験片の幅は６ｍｍであり、試験片の厚さは、試験片ごとにダイヤルゲージにより測定した。 The tensile strength was a value obtained by dividing the maximum load load (N) when the PTFE porous membrane was ruptured by the tensile test by the cross-sectional area (mm 2 ) of the PTFE porous membrane before the tensile test. In addition, the width | variety of the test piece was 6 mm, and the thickness of the test piece was measured for each test piece with the dial gauge.
　［突き刺し強度］
　ＰＴＦＥ多孔質膜の突き刺し強度は、以下のように求めた。 [Puncture strength]
The puncture strength of the PTFE porous membrane was determined as follows.
　最初に、両面テープ（３０ｍｍ×３０ｍｍの正方形）の中央部をφ１６ｍｍで丸く打ち抜き、打ち抜いた部分に、測定対象であるＰＴＦＥ多孔質膜を、当該膜にしわが入らないように貼り付けた。次に、圧縮試験機（カトーテック社製、ＫＥＳ－Ｇ５）を用いて、ＰＴＦＥ多孔質膜の露出部分に針（針径２．０ｍｍ）を突き刺し（突き刺し速度２ｃｍ／秒）、その際に測定された荷重変位曲線から最大荷重を読み取って、これを針径で除した値を突き刺し強度（ｋＰａ）とした。突き刺し試験は２５℃で行った。 First, the center part of a double-sided tape (30 mm × 30 mm square) was punched out with a diameter of 16 mm, and a PTFE porous film to be measured was attached to the punched part so as not to wrinkle the film. Next, using a compression tester (Kato Tech Co., Ltd., KES-G5), the exposed part of the PTFE porous membrane was pierced with a needle (needle diameter of 2.0 mm) (the piercing speed was 2 cm / sec), and measurement was performed at that time The maximum load was read from the obtained load displacement curve, and the value obtained by dividing the maximum load by the needle diameter was defined as the piercing strength (kPa). The piercing test was performed at 25 ° C.
　［耐水圧］
　ＰＴＦＥ多孔質膜の耐水圧は、ＪＩＳ　Ｌ１０９２に記載されている耐水度試験機（高水圧法）を用いて求めた。ただし、ＪＩＳ　Ｌ１０９２に規定の面積では膜が著しく変形するため、ステンレスメッシュ（開口径２ｍｍ）を膜の加圧面の反対側に設置し、変形を抑制した状態で測定した。 [Water pressure resistance]
The water pressure resistance of the PTFE porous membrane was determined using a water resistance tester (high water pressure method) described in JIS L1092. However, since the film was remarkably deformed in the area defined in JIS L1092, a stainless steel mesh (opening diameter 2 mm) was placed on the opposite side of the pressure surface of the film, and measurement was performed in a state where deformation was suppressed.
　［耐水圧保持試験］
　ＰＴＦＥ多孔質膜の耐水圧保持試験は、耐水圧試験と同じく、ＪＩＳ　Ｌ１０９２に記載されている耐水度試験機を用いて行った。具体的には、１５０ｋＰａの水圧（深度１５ｍの水圧に相当する）をＰＴＦＥ多孔質膜に印加し、１時間保持した後に水漏れの有無を観察し、良否判定を行った。ただし、ＪＩＳ　Ｌ１０９２に規定の面積では膜が著しく変形するため、ステンレスメッシュ（開口径３ｍｍ）を膜の加圧面の反対側に設置し、変形をある程度抑制した状態で測定した。良否の判定基準は次の通りである。
　１：水漏れ無し
　２：３０分～１時間の間にごく僅かな水漏れが発生
　３：３０分以内に水漏れが発生
　４：破裂 [Water pressure retention test]
The water pressure resistance holding test of the PTFE porous membrane was performed using a water resistance tester described in JIS L1092, similarly to the water pressure resistance test. Specifically, a water pressure of 150 kPa (corresponding to a water pressure of a depth of 15 m) was applied to the PTFE porous membrane, and after holding for 1 hour, the presence or absence of water leakage was observed to determine pass / fail. However, since the film was remarkably deformed in the area defined in JIS L1092, the measurement was performed with a stainless mesh (opening diameter: 3 mm) placed on the opposite side of the pressure surface of the film and the deformation was suppressed to some extent. The acceptance criteria are as follows.
1: No water leak 2: A slight water leak occurred between 30 minutes and 1 hour 3: A water leak occurred within 30 minutes 4: Burst
　（実施例１）
　ＰＴＦＥ微粉末（ダイキン工業社製　ポリフロンＦ１０１ＨＥ）１００重量部と、液状潤滑剤（ナフサ）２０重量部とを均一に混練し、ＰＴＦＥ微粉末とナフサとを含むペーストを準備した。このペーストを２０ｋｇ／ｃｍ2の条件で円筒状に予備成形した。次に、得られた円筒状の予備成形体を押出成形し、シート状の成形体を得た。得られたシート状の成形体の引張強度を測定したところ（測定にあたっては、チャック間距離１０ｍｍ、サンプル幅１０ｍｍとした）、長手方向（ＭＤ）、幅方向（ＴＤ）ともに、１．８ＭＰａであった。 Example 1
PTFE fine powder (Daikin Kogyo Polyflon F101HE) 100 parts by weight and liquid lubricant (naphtha) 20 parts by weight were uniformly kneaded to prepare a paste containing PTFE fine powder and naphtha. This paste was preformed into a cylindrical shape under the condition of 20 kg / cm 2 . Next, the obtained cylindrical preform was extrusion molded to obtain a sheet-like molded body. When the tensile strength of the obtained sheet-like molded body was measured (in the measurement, the distance between chucks was 10 mm and the sample width was 10 mm), the longitudinal direction (MD) and the width direction (TD) were both 1.8 MPa. It was.
　次に、シート状の成形体を、液状潤滑剤を含んだ状態で１対の金属圧延ロールの間に通し、厚さ２００μｍの長尺シートを得た。この長尺シートを温度１５０℃の乾燥機内に５分間滞留するように連続的に通して液状潤滑剤を乾燥除去し、ＰＴＦＥシートを作製した。 Next, the sheet-like formed body was passed between a pair of metal rolling rolls containing a liquid lubricant to obtain a long sheet having a thickness of 200 μm. The long sheet was continuously passed in a dryer at a temperature of 150 ° C. for 5 minutes so as to dry and remove the liquid lubricant, and a PTFE sheet was produced.
　用いたＰＴＦＥ微粉末の数平均分子量を標準比重法により算出したところ、１．１×１０8であった。 It was 1.1 * 10 < 8 > when the number average molecular weight of the used PTFE fine powder was computed by the standard specific gravity method.
　上記のように作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に１３倍延伸した。さらに、長手方向に延伸したＰＴＦＥシートを４枚重ね合わせ、テンター法により１５０℃の雰囲気温度で幅方向に４５倍延伸した。その後、二軸延伸したＰＴＦＥシートを焼成し（焼成温度４００℃、以降の実施例および比較例においても同じ）、４層構造を有するＰＴＦＥ多孔質膜を得た。 The PTFE sheet produced as described above was stretched 13 times in the longitudinal direction in a dryer at an atmospheric temperature of 290 ° C. Further, four PTFE sheets stretched in the longitudinal direction were overlapped and stretched 45 times in the width direction at an atmospheric temperature of 150 ° C. by a tenter method. Thereafter, the biaxially stretched PTFE sheet was fired (firing temperature of 400 ° C., the same in the following examples and comparative examples) to obtain a PTFE porous membrane having a four-layer structure.
　（実施例２）
　実施例１で作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に８倍延伸した。さらに、長手方向に延伸したＰＴＦＥシートを２枚重ね合わせ、テンター法により１５０℃の雰囲気温度で幅方向に３１．５倍延伸した。その後、二軸延伸したＰＴＦＥシートを焼成し、２層構造を有するＰＴＦＥ多孔質膜を得た。 (Example 2)
The PTFE sheet produced in Example 1 was stretched 8 times in the longitudinal direction in a dryer having an atmospheric temperature of 290 ° C. Further, two PTFE sheets stretched in the longitudinal direction were superposed and stretched 31.5 times in the width direction at an ambient temperature of 150 ° C. by a tenter method. Thereafter, the biaxially stretched PTFE sheet was fired to obtain a PTFE porous membrane having a two-layer structure.
　（実施例３）
　実施例１で作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に１０倍延伸し、さらに、テンター法により１５０℃の雰囲気温度で幅方向に６０倍延伸した。その後、二軸延伸したＰＴＦＥシートを３枚重ね合わせて焼成し、３層構造を有するＰＴＦＥ多孔質膜を得た。 (Example 3)
The PTFE sheet produced in Example 1 was stretched 10 times in the longitudinal direction in a dryer at an ambient temperature of 290 ° C., and further stretched 60 times in the width direction at an ambient temperature of 150 ° C. by a tenter method. Thereafter, three biaxially stretched PTFE sheets were stacked and fired to obtain a PTFE porous membrane having a three-layer structure.
　（実施例４）
　実施例１で作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に６．５倍延伸した。さらに、長手方向に延伸したＰＴＦＥシートを２枚重ね合わせ、テンター法により１５０℃の雰囲気温度で幅方向に４５倍延伸した。その後、二軸延伸したＰＴＦＥシートを焼成し、２層構造を有するＰＴＦＥ多孔質膜を得た。 Example 4
The PTFE sheet produced in Example 1 was stretched 6.5 times in the longitudinal direction in a dryer at an ambient temperature of 290 ° C. Further, two PTFE sheets stretched in the longitudinal direction were overlapped and stretched 45 times in the width direction at an ambient temperature of 150 ° C. by a tenter method. Thereafter, the biaxially stretched PTFE sheet was fired to obtain a PTFE porous membrane having a two-layer structure.
　（比較例１）
　実施例１で作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に６倍延伸し、さらに、テンター法により１５０℃の雰囲気温度で幅方向に２０倍延伸した。その後、これを焼成して、単層のＰＴＦＥ多孔質膜を得た。 (Comparative Example 1)
The PTFE sheet produced in Example 1 was stretched 6 times in the longitudinal direction in a dryer at an ambient temperature of 290 ° C., and further stretched 20 times in the width direction at an ambient temperature of 150 ° C. by a tenter method. Then, this was baked and the single layer PTFE porous membrane was obtained.
　（比較例２）
　実施例１で作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に４倍延伸し、さらに、テンター法により１５０℃の雰囲気温度で幅方向に２０倍延伸した。その後、これを焼成して、単層のＰＴＦＥ多孔質膜を得た。 (Comparative Example 2)
The PTFE sheet produced in Example 1 was stretched 4 times in the longitudinal direction in a dryer at an ambient temperature of 290 ° C., and further stretched 20 times in the width direction at an ambient temperature of 150 ° C. by a tenter method. Then, this was baked and the single layer PTFE porous membrane was obtained.
　（比較例３）
　ＰＴＦＥ微粉末（ダイキン工業社製　ポリフロンＦ１０１ＨＥ）の代わりに、別のＰＴＦＥ微粉末（ダイキン工業社製　ポリフロンＦ１０４）を用いた以外は実施例１と同様にして、ＰＴＦＥシートを作製した。用いたＰＴＦＥ微粉末の数平均分子量を標準比重法により算出したところ、４．０×１０7であった。 (Comparative Example 3)
A PTFE sheet was produced in the same manner as in Example 1 except that another PTFE fine powder (Polyflon F104 made by Daikin Industries, Ltd.) was used instead of the PTFE fine powder (Polyflon F101HE made by Daikin Industries, Ltd.). It was 4.0 * 10 < 7 > when the number average molecular weight of the used PTFE fine powder was computed by the standard specific gravity method.
　上記のように作製したＰＴＦＥシートを、２９０℃の雰囲気温度の乾燥機中で長手方向に１３倍延伸した。さらに、長手方向に延伸したＰＴＦＥシートを４枚重ね合わせ、テンター法により１５０℃の雰囲気温度で幅方向に４５倍延伸した。その後、二軸延伸したＰＴＦＥシートを焼成し、４層構造を有するＰＴＦＥ多孔質膜を得た。 The PTFE sheet produced as described above was stretched 13 times in the longitudinal direction in a dryer at an atmospheric temperature of 290 ° C. Further, four PTFE sheets stretched in the longitudinal direction were overlapped and stretched 45 times in the width direction at an atmospheric temperature of 150 ° C. by a tenter method. Thereafter, the biaxially stretched PTFE sheet was fired to obtain a PTFE porous membrane having a four-layer structure.
　実施例１～４および比較例１～３で作製したＰＴＦＥ多孔質膜の延伸倍率、多孔質層積層数、膜厚、平均孔径および気孔率を表１に、その他の諸特性の評価結果を表２に示す。 Table 1 shows the stretching ratio, the number of porous layers laminated, the film thickness, the average pore diameter and the porosity of the PTFE porous membranes prepared in Examples 1 to 4 and Comparative Examples 1 to 3, and the evaluation results of other properties are shown in Table 1. It is shown in 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１、２に示すように、全てのＰＴＦＥ多孔質膜における面密度はほぼ同等となり、全サンプルがほぼ同レベルの通音性を有していると考えられる。しかし、標準比重法により算出した数平均分子量が４．０×１０7のＰＴＦＥを用いた比較例３では、多層構造であるにもかかわらず、その防水性（耐水圧性）が大きく低下した。また、比較例１、２は、実施例と同じＰＴＦＥを用いているものの単層構造であるため、その防水性（耐水圧性）が低くなった。面密度が同程度であっても、多層構造を有する実施例の方が高い防水性を示すことがわかる。また、実施例の各多孔質膜を比較すると、積層数が増加するにつれて防水性が高くなる傾向を示した。 As shown in Tables 1 and 2, the surface densities of all the PTFE porous membranes are almost equal, and it is considered that all samples have substantially the same level of sound permeability. However, in Comparative Example 3 using PTFE having a number average molecular weight of 4.0 × 10 7 calculated by the standard specific gravity method, the waterproofness (water pressure resistance) was greatly reduced despite the multilayer structure. Moreover, since the comparative examples 1 and 2 used the same PTFE as an Example but are single layer structures, the waterproofness (water pressure resistance) became low. It can be seen that even if the surface density is similar, the example having the multilayer structure shows higher waterproofness. Moreover, when each porous membrane of an Example was compared, the tendency for waterproofness to become high was shown as the number of lamination | stacking increased.
　本発明は、その意図および本質的な特徴から逸脱しない限り、他の実施形態に適用しうる。この明細書に開示されている実施形態は、あらゆる点で説明的なものであってこれに限定されない。本発明の範囲は、上記説明ではなく添付したクレームによって示されており、クレームと均等な意味および範囲にあるすべての変更はそれに含まれる。 The present invention can be applied to other embodiments without departing from the intent and essential features thereof. The embodiments disclosed in this specification are illustrative in all respects and are not limited thereto. The scope of the present invention is shown not by the above description but by the appended claims, and all modifications that fall within the meaning and scope equivalent to the claims are embraced therein.
　本発明の防水通音膜は、例えば、音声機能を備えた電気製品の通音性を確保したまま、当該製品に高い防水性を付与できる。本発明の防水通音膜は、その高い防水性から、海岸、森林など、近年、使用場所が通常の屋内外から大きく広がりつつある電気製品への使用に好適である。 The waterproof sound-permeable membrane of the present invention can give a high waterproof property to the product while ensuring the sound-permeable property of an electric product having a voice function, for example. The waterproof sound-permeable membrane of the present invention is suitable for use in electrical products such as beaches and forests, where the place of use is spreading widely from ordinary indoors and outdoors in recent years due to its high waterproofness.

Claims (6)

  1. 　ポリテトラフルオロエチレン（ＰＴＦＥ）多孔質膜を含む防水通音膜であって、
    　前記ＰＴＦＥ多孔質膜は、第１多孔質層と、ＰＴＦＥのマトリクス間に働く結着力に基づいて前記第１多孔質層と積層および一体化された第２多孔質層と、を備え、
    　前記第１および第２多孔質層は、標準比重法により算出した数平均分子量が５．０×１０7以上のＰＴＦＥにより構成され、
    　前記第１および第２多孔質層から選ばれる少なくとも１つの層の平均孔径が１μｍ以下であり、
    　前記防水通音膜の面密度が１～１０ｇ／ｍ2であり、
    　前記防水通音膜の引張強度が１０～１００ＭＰａであり、
    　前記防水通音膜の突き刺し強度を前記防水通音膜の面密度で除した値が、２５～５０ｋＰａ・ｍ2／ｇである防水通音膜。     A waterproof sound-permeable membrane comprising a polytetrafluoroethylene (PTFE) porous membrane,
    The PTFE porous membrane includes a first porous layer, and a second porous layer laminated and integrated with the first porous layer based on a binding force acting between the PTFE matrices,
    The first and second porous layers are composed of PTFE having a number average molecular weight calculated by a standard specific gravity method of 5.0 × 10 7 or more,
    An average pore diameter of at least one layer selected from the first and second porous layers is 1 μm or less;
    The surface density of the waterproof sound-permeable membrane is 1 to 10 g / m 2 ;
    The waterproof sound-permeable membrane has a tensile strength of 10 to 100 MPa,
    A waterproof sound-permeable membrane having a value obtained by dividing the puncture strength of the waterproof sound-permeable membrane by the surface density of the waterproof sound-permeable membrane is 25 to 50 kPa · m 2 / g.
  2. 　前記第１および第２多孔質層は、それぞれ二軸延伸された層であり、
    　前記第１および第２多孔質層の延伸倍率が互いに等しい、請求項１に記載の防水通音膜。     The first and second porous layers are respectively biaxially stretched layers,
    The waterproof sound-permeable membrane according to claim 1, wherein the stretching ratios of the first and second porous layers are equal to each other.
  3. 　前記第１および第２多孔質層の延伸方向が互いに一致するとともに、前記第１および第２多孔質層の延伸倍率が、各延伸方向に関して互いに等しい、請求項２に記載の防水通音膜。 The waterproof sound-permeable membrane according to claim 2, wherein the stretching directions of the first and second porous layers coincide with each other, and the stretching ratios of the first and second porous layers are equal to each other in each stretching direction.
  4. 　請求項１に記載の防水通音膜の製造方法であって、
    　標準比重法により算出した数平均分子量が５．０×１０7以上のポリテトラフルオロエチレン（ＰＴＦＥ）からなるＰＴＦＥ微粉末と、加工助剤と、を含むペーストを押出成形する工程と、
    　前記ペーストの成形体であるシートまたは前記ペーストの成形体を圧延して得られるシートを、ＰＴＦＥの融点未満の温度で第１方向に延伸する工程と、
    　前記第１方向への延伸後のシートを、複数枚重ね合わせる工程と、
    　前記重ね合わせた複数枚のシートを、ＰＴＦＥの融点未満の温度で前記第１方向と交差する第２方向に延伸する工程と、
    　前記第２方向への延伸後の複数枚のシートを、ＰＴＦＥの融点以上の温度で焼成して、ＰＴＦＥのマトリクス間に働く結着力に基づいて一体化する工程と、を含む、防水通音膜の製造方法。     A method for producing a waterproof sound-permeable membrane according to claim 1,
    A step of extruding a paste containing PTFE fine powder made of polytetrafluoroethylene (PTFE) having a number average molecular weight of 5.0 × 10 7 or more calculated by the standard specific gravity method, and a processing aid;
    Stretching a sheet that is a molded body of the paste or a sheet obtained by rolling the molded body of the paste in a first direction at a temperature lower than the melting point of PTFE;
    A step of superimposing a plurality of sheets stretched in the first direction;
    Stretching the superposed sheets in a second direction intersecting the first direction at a temperature lower than the melting point of PTFE;
    A step of firing the plurality of sheets after being stretched in the second direction at a temperature equal to or higher than the melting point of PTFE and integrating them based on the binding force acting between the PTFE matrices. Manufacturing method.
  5. 　請求項１に記載の防水通音膜の製造方法であって、
    　標準比重法により算出した数平均分子量が５．０×１０7以上のポリテトラフルオロエチレン（ＰＴＦＥ）からなるＰＴＦＥ微粉末と、加工助剤と、を含むペーストを押出成形する工程と、
    　前記ペーストの成形体であるシートまたは前記ペーストの成形体を圧延して得られるシートを、ＰＴＦＥの融点未満の温度で二軸延伸する工程と、
    　前記二軸延伸後のシートを、複数枚重ね合わせる工程と、
    　前記重ね合わせた複数枚のシートを、ＰＴＦＥの融点以上の温度で焼成して、ＰＴＦＥのマトリクス間に働く結着力に基づいて一体化する工程と、を含む、防水通音膜の製造方法。     A method for producing a waterproof sound-permeable membrane according to claim 1,
    A step of extruding a paste containing PTFE fine powder made of polytetrafluoroethylene (PTFE) having a number average molecular weight of 5.0 × 10 7 or more calculated by the standard specific gravity method, and a processing aid;
    Biaxially stretching a sheet that is a molded body of the paste or a sheet obtained by rolling the molded body of the paste at a temperature lower than the melting point of PTFE;
    A step of superimposing a plurality of sheets after biaxial stretching;
    A method of manufacturing a waterproof sound-permeable membrane, comprising: baking the plurality of stacked sheets at a temperature equal to or higher than the melting point of PTFE and integrating them based on a binding force acting between the PTFE matrices.
  6. 　音声機能を備えた電気製品であって、
    　音声を出力するための発音部および音声を入力するための受音部から選ばれる少なくとも１つと、前記発音部および／または受音部と外部との間で音声を伝達できるとともに、前記発音部および／または受音部への水の侵入を抑制する防水通音膜と、を備え、
    　前記防水通音膜が請求項１に記載の防水通音膜である、電気製品。     An electrical product with a voice function,
    Sound can be transmitted between the sound generation unit and / or the sound receiving unit and the outside, and at least one selected from a sound generation unit for outputting sound and a sound receiving unit for inputting sound, and the sound generation unit and And / or a waterproof sound-permeable membrane that suppresses the entry of water into the sound receiving unit,
    An electrical product, wherein the waterproof sound-permeable membrane is the waterproof sound-permeable membrane according to claim 1.
PCT/JP2010/050711 2009-01-21 2010-01-21 Waterproofing sound-transmitting film, process for producing same, and electrical product employing same WO2010084912A1 (en)

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US13/009,510 US8272517B2 (en) 2009-01-21 2011-01-19 Water-proof sound-transmitting membrane, method for producing the water-proof sound-transmitting membrane, and electrical appliance including the water-proof sound-transmitting membrane

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